Pholcus phalangioides
Sam Droege · CC0Harmless. The old story that it has the most powerful venom of any spider but fangs too short to use is simply untrue — it has neither. It is one of the most useful spiders to have indoors.
A cellar spider is most often confused with a species that is medically significant. If you are trying to rule those out, check these:
Across the whole United States and most of the world, having spread with people. If you have a building with a quiet ceiling corner, you have these.
Ceiling corners, cellars, garages and quiet rooms, year-round indoors.
It hangs upside-down in a loose tangle of web and stays there. Its famous trick is to whirl: when something touches the web it vibrates so fast that it blurs into near-invisibility, which makes it very hard for a predator to grab. It is also a spider-eater. Cellar spiders regularly kill and eat other spiders, including much larger ones, by throwing silk from a safe distance. A house with cellar spiders in it tends to have fewer of everything else.
Leave it. This is the single most useful spider you can have indoors, and the webs are easier to clear than the insects it removes. If you want the cobwebs gone, a vacuum takes both web and spider without any need to touch anything.
No. It is untrue in both halves: their venom is not exceptionally potent, and their fangs are perfectly capable of piercing skin. They simply have no interest in biting people, and there is no record of one causing harm.
Both get called daddy long legs and they are not closely related. A cellar spider is a true spider with two body sections and a web. A harvestman has a single oval body, no web, no silk and no venom at all.
It is a defence. Whirling fast enough to blur its outline makes it very difficult for a bird or a wasp to target, and it costs the spider nothing.
Yes, routinely, including species considerably larger than themselves. They invade other webs and throw silk from out of reach. It is a large part of why they are worth keeping.
Identify another animal from a photo or return to the Spiders guide.
Last reviewed 2026-07-29. We identify, we don’t diagnose — what we can and can’t tell you.